1. Field of the Invention
This invention relates to a structure of a plasma display panel in which a display image is generated by means of producing a discharge between a pair of electrodes on which a dielectric layer overlays.
The present application claims priority from Japanese Application No. 2000-257442, the disclosure of which is incorporated herein by reference for all purposes.
2. Description of the Related Art
A plasma display panel (hereinafter referred to as xe2x80x9cPDPxe2x80x9d) serving as an oversize and slim image display panel is used in a public display unit such as in a television receiver, an information board or a display board. A surface discharge scheme AC type of PDP is commercially manufactured.
The surface discharge scheme AC type PDP includes, as illustrated in FIG. 17, a front glass substrate 1 and a back glass substrate 4 which is placed opposite to the front glass substrate 1 with a discharge space in between. The front glass substrate 1 has the inner face on which row electrode pairs (Xxe2x80x2, Yxe2x80x2), a dielectric layer 2 overlaying the row electrode pairs (Xxe2x80x2, Yxe2x80x2), and a protective layer 3 for protecting the dielectric layer 2 are provided, while the back glass substrate 4 has the interior surface on which column electrodes Dxe2x80x2, phosphor layers 6R, 6G, 6B individually overlaying the column electrodes Dxe2x80x2, and partition walls 5 partitioning a discharge space are provided, in which discharge cells are formed at particular intersecting areas of the row electrode pairs (Xxe2x80x2, Yxe2x80x2) and the column electrodes Dxe2x80x2.
With the above PDP, a discharge (opposite discharge) is caused selectively between one of the row electrode pair (Xxe2x80x2, Yxe2x80x2) and the column electrode Dxe2x80x2 in each discharge cell, to scatter lighted cells (the discharge cell in which wall charge is formed on the dielectric layer 2) and nonlighted cells (the discharge cell in which wall charge is not formed on the dielectric layer 2) over the panel surface. After that, in all the display lines L, discharge sustaining pulses are applied to the row electrodes Xxe2x80x2, Yxe2x80x2 in unison, to produce a sustain discharge (surface discharge) in the lighted cells.
Hence, the discharge gas filled in the discharge space generates ultraviolet radiation. The ultraviolet radiation causes the red phosphor layer 6R and/or the green phosphor layer 6G and/or the blue phosphor layer 6B, colors of which serves as the primary colors and which are formed in the corresponding discharge cells, to emit light to form an image on the panel.
In the PDP, interelectrode capacitance in each discharge cell is formed by the row electrode pair (Xxe2x80x2, Yxe2x80x2) and dielectric layer 2, and by the row electrode pair (Xxe2x80x2, Yxe2x80x2) and front glass substrate 1.
In the conventional PDP, a relative dielectric constant of the front glass substrate 1 is the order of eight, which is set at a relatively high value.
This produces a problem in which when the discharge sustaining pulses are applied alternately between a pair of the row electrodes Xxe2x80x2 and Yxe2x80x2 to produce the sustain discharge (surface discharge), a larger interelectrode capacitance formed by the row electrode pair (Xxe2x80x2, Yxe2x80x2) and the front glass substrate 1 results in an increase of reactive power (electric power which does not work on light emission).
The conventional PDP has a problem in which the reactive power further increases when a higher voltage of the discharge sustaining pulse is supplied for high-voltage driving in order to increase the efficiency of light emission.
The present invention has been made to solve the problems associated with the surface discharge scheme alternating current type plasma display panel as described above.
It is therefore an object of the present invention to provide a plasma display panel which allows reduction in reactive power when a sustain discharge is produced, while allowing high-voltage driving.
To attain the above object, a plasma display panel according to a first aspect of the present invention includes a pair of substrates which face each other with a discharge space in between and one of which has an inner face on which row electrode pairs each opposing each other with a discharge gap in between, and a dielectric layer overlaying the row electrode pairs relative to the discharge space are provided. Such plasma display panel features in that a low dielectric constant layer having a relative dielectric constant lower than that of the above-described one substrate is provided between the above-described one substrate and the row electrode pair.
In the plasma display panel according to the first aspect, interelectrode capacitance in each of unit light emitting areas is formed by the row electrode pair and dielectric layer and the row electrode pair and above-described one substrate, and additionally, by the low dielectric constant layer which is provided between the above-described one substrate and the row electrode pair.
With the plasma display panel, addressing operation is performed in order to scatter the lighted unit light emitting areas (the unit light emitting area in which wall charge is formed on the dielectric layer) and the nonlighted unit light emitting areas (the unit light emitting area in which wall charge is not formed on the dielectric layer) over the panel surface in accordance with an image to be displayed.
Then, discharge sustaining pulses are applied to the row electrode pairs to cause a sustain discharge (surface discharge) in each lighted unit light emitting area.
At this time, reactive power (electric power does not work on light emission) occurs due to the interelectrode capacitance formed by the row electrode pair and above-described one substrate.
However, by providing the low dielectric constant layer between the row electrode pair and the above-described one substrate, it is possible to decrease in thickness of portion of the above-described one substrate which faces the row electrode pair as compared with that of a conventional substrate. Further, since the low dielectric constant layer has a relative dielectric constant lower than that of the above-described one substrate, it is possible to reduce the interelectrode capacitance inducing the reactive power.
In consequence, according to the first aspect, the amount of reactive power occurring when the sustain discharge is produced for generating an image can be reduced as compared with the conventional plasma display panel. Further, the reactive power can be reduced even when a higher voltage of the discharge sustaining pulse is supplied for high-voltage driving in order to increase the efficiency of light emission.
To attain the aforementioned object, the plasma display panel according to a second aspect features, in addition to the configuration of the first aspect, in that the relative dielectric constant of the low dielectric constant layer is six or less.
With this configuration, the relative dielectric constant of the low dielectric constant layer is set at a value lower than a value of a relative dielectric constant of the substrate which is typically the order of eight.
This allows reduction in reactive power occurring when the sustain discharge is produced for forming the image as compared with the conventional plasma display panel. Additionally, even when a higher voltage of the discharge sustaining pulse is supplied for high-voltage driving in order to increase in the efficiency of light emission, the reactive power can be reduced.
To attain the aforementioned object, the plasma display panel according to a third aspect features, in addition to the configuration of the first aspect, in that the low dielectric constant layer includes SiO2. With the configuration, the relative dielectric constant of the low dielectric constant layer can be set at a value lower than that of the relative dielectric constant of the substrate.
To attain the aforementioned object, the plasma display panel according to a fourth aspect features, in addition to the configuration of the first aspect, in that the above-described one substrate is a front substrate placed on the display surface side of the panel and in that the low dielectric constant layer is formed of light-transmittable materials.
According to the plasma display panel of the fourth aspect, the interelectrode capacitance formed by the front substrate and the row electrode pair is decreased due to the low dielectric constant layer provided between the front substrate and the row electrode pair. Additionally, since the low dielectric constant layer is formed of the light-transmittable materials, the provision of the low dielectric constant layer may not inhibit the generation of images.
To attain the aforementioned object, the plasma display panel according to a fifth aspect features, in addition to the configuration of the first aspect, in that the low dielectric constant layer is provided over almost the entire inner face of the one substrate. With the configuration, the interelectrode capacitance formed by the row electrode pairs and the one substrate can be sufficiently reduced.
To attain the aforementioned object, the plasma display panel according to a sixth aspect features, in addition to the configuration of the fifth aspect, in that the low dielectric constant layer is provided on the inner face of the aforementioned one substrate except on at least a portion opposite to a discharge gap between each of the row electrode pairs.
According to the plasma display panel of the sixth aspect, when the sustain discharge is produced for generating the image, as the interelectrode capacitance formed by the row electrode pair and the one substrate is reduced due to the provision of the low dielectric constant layer, the reactive power reduces.
In this point, since the low dielectric constant layer is provided on portions except the portion opposite to the discharge gap between the row electrode pair, and a pair of the row electrodes oppose each other through the dielectric layer having a large relative dielectric constant, a distance for producing a discharge is shorter, resulting in decreasing a voltage for starting the discharge.
To attain the aforementioned object, the plasma display panel according to a seventh aspect features, in addition to the configuration of the first aspect, in that the low dielectric constant layer is provided only on a portion, opposite to each of the row electrode pairs, of portions of the inner face of the aforementioned one substrate which is opposite the discharge space.
With the configuration, since a pair of the row electrodes oppose each other through the dielectric layer having a large relative dielectric constant, a distance for producing the discharge is shorter, resulting in decreasing a voltage for starting the discharge. Additionally, since the low dielectric constant layer is divided to decrease the area of the continuous portion, the low dielectric constant layer is protected from cracking.
To attain the aforementioned object, the plasma display panel according to an eighth aspect features, in addition to the configuration of the first aspect, in that the low dielectric constant layer is formed in an island shape in each row electrode pair so as to separate it from other low dielectric constant layer.
With this configuration, the low dielectric constant layer is divided to decrease the area of the continuous portion. Hence, the low dielectric constant layer is protected from cracking.
To attain the aforementioned object, the plasma display panel according to a ninth aspect features, in addition to the configuration of the first aspect, in that the low dielectric layer is provided on portions of the inner face of the aforementioned one substrate except on a portion facing a portion between adjacent row electrode pairs, and in that a light absorption layer is provided on the portion, facing the portion between the adjacent row electrode pairs, of the inner face of the one substrate.
With this configuration, the reflection of ambient light incident upon the non-light emitting area on the panel surface is prevented, resulting in the prevention of inferior contrast on the screen.